전력 스위칭 트랜지스터 크기 가변을 이용한 듀얼모드 DC-DC 벅 변환기 설계

In this paper, we design a dual mode buck converter using power transistor width scaling to improve the light load efficiency. The DC-DC converter adopts the SFM mode in light load and the PWM mode in heavy load using the VCO (voltage controlled oscillator) as a dual mode. Also the power transistor width is varied according to the load current to enhance the power efficiency, which is designed with a small circuit including the VCO used in the dual mode. The proposed circuit has been realized with the Magnachip 0.35m CMOS process and simulated using Spectre. The simulation results show that the power efficiency of the proposed converter has 86.8% ∼ 91.5% for 20mA ∼ 250mA output load current, which shows 3.7% ∼ 10.8% higher than that of previous buck converters.